collision_monitor_node.launch.py

#!/usr/bin/env python3
 
# Copyright (c) 2022 Samsung R&D Institute Russia
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
 
import os
 
from ament_index_python.packages import get_package_share_directory
 
from launch import LaunchDescription
from launch.actions import DeclareLaunchArgument
from launch.substitutions import LaunchConfiguration
from launch_ros.actions import Node
from launch_ros.descriptions import ParameterFile
from nav2_common.launch import RewrittenYaml
 
 
def generate_launch_description():
    # Environment
    package_dir = get_package_share_directory('nav2_collision_monitor')
 
    # Constant parameters
    lifecycle_nodes = ['collision_monitor']
    autostart = True
 
    # Launch arguments
    # 1. Create the launch configuration variables
    namespace = LaunchConfiguration('namespace')
    use_sim_time = LaunchConfiguration('use_sim_time')
    params_file = LaunchConfiguration('params_file')
 
    # 2. Declare the launch arguments
    declare_namespace_cmd = DeclareLaunchArgument(
        'namespace',
        default_value='',
        description='Top-level namespace')
 
    declare_use_sim_time_cmd = DeclareLaunchArgument(
        'use_sim_time',
        default_value='True',
        description='Use simulation (Gazebo) clock if true')
 
    declare_params_file_cmd = DeclareLaunchArgument(
        'params_file',
        default_value=os.path.join(package_dir, 'params', 'collision_monitor_params.yaml'),
        description='Full path to the ROS2 parameters file to use for all launched nodes')
 
    # Create our own temporary YAML files that include substitutions
    param_substitutions = {
        'use_sim_time': use_sim_time}
 
    configured_params = ParameterFile(
        RewrittenYaml(
            source_file=params_file,
            root_key=namespace,
            param_rewrites=param_substitutions,
            convert_types=True),
        allow_substs=True)
 
    # Nodes launching commands
    start_lifecycle_manager_cmd = Node(
            package='nav2_lifecycle_manager',
            executable='lifecycle_manager',
            name='lifecycle_manager',
            output='screen',
            emulate_tty=True,  # https://github.com/ros2/launch/issues/188
            parameters=[{'use_sim_time': use_sim_time},
                        {'autostart': autostart},
                        {'node_names': lifecycle_nodes}])
 
    start_collision_monitor_cmd = Node(
            package='nav2_collision_monitor',
            executable='collision_monitor',
            output='screen',
            emulate_tty=True,  # https://github.com/ros2/launch/issues/188
            parameters=[configured_params])
 
    ld = LaunchDescription()
 
    # Launch arguments
    ld.add_action(declare_namespace_cmd)
    ld.add_action(declare_use_sim_time_cmd)
    ld.add_action(declare_params_file_cmd)
 
    # Node launching commands
    ld.add_action(start_lifecycle_manager_cmd)
    ld.add_action(start_collision_monitor_cmd)
 
    return ld